A wheel bearing apparatus that supports a wheel of a vehicle relative to a suspension apparatus and that incorporates a wheel speed detecting apparatus to detect a rotational speed of a wheel of a vehicle to control the anti-lock braking system (ABS) is generally known. Such a bearing apparatus generally includes a sealing apparatus between an inner member and an outer member. The inner and outer members are rotatable relatively to each other via rolling elements (balls) between the two. A magnetic encoder has alternately arranged magnetic poles along its circumference and is integrated into the sealing apparatus. A wheel speed detecting sensor detects the variation in magnetic poles of the magnetic encoder according to the rotation of the wheel.
The wheel speed sensor is usually mounted on a knuckle after the wheel bearing apparatus is mounted on the knuckle to form a suspension apparatus. Recently, however, a wheel bearing apparatus incorporating a wheel speed detecting apparatus has been proposed where the wheel speed detecting sensor is self-contained within the wheel bearing. This reduces the size of the wheel bearing apparatus as well as eliminates troublesome in air gap adjustment between the wheel speed sensor and the magnetic encoder.
An example of a prior art wheel bearing apparatus incorporating a wheel speed detecting apparatus is shown in FIG. 15. This wheel bearing apparatus incorporating a wheel speed detecting apparatus 100 includes an outer member 101, an inner member 103, inserted into the outer member via double row balls 102, and a wheel speed detecting apparatus 104, mounted on one end of the outer member.
The outer member 101 is integrally formed with a body mounting flange on its outer circumference. The body mounting flange 101b is to be mounted on a knuckle (not shown) to form a portion of a suspension of a vehicle. The outer member inner circumference includes double row outer raceway surfaces 101a, 101a. 
The inner member 103 includes a wheel hub 105 and an inner ring 106 secured on the wheel hub 105. The wheel hub 105 is formed at one end with a wheel mounting flange 107 to mount a wheel (not shown). The wheel hub outer circumference has one inner raceway surface 105a that oppose one of the double row outer raceway surfaces 101a, 101a. A cylindrical portion 105b extends from the inner raceway surface 105a. The inner ring 106 is formed with the other inner raceway surfaces 106a on its outer circumference. The other inner raceway surface 106a opposes the other of the double row outer raceway surfaces 101a, 101a. The inner ring 106 is press-fit onto the cylindrical portion 105b of the wheel hub 105 via a predetermined interface.
Double row balls 102, 102 are contained between the double row outer raceway surfaces 101a, 101a and the inner raceway surface 105a, 106a, respectively, of the wheel hub 105 and the inner ring 106. The balls 102, 102 are rollably held by cages 108, 108. In addition, seals 109, 110 are mounted in annular openings formed between the outer member 101 and the inner member 103. The seals 109, 110 prevent leakage of grease contained in the bearing and entry of rainwater or dusts from the outside.
The wheel speed detecting apparatus 104, as shown in FIG. 16, includes a sensor holder 112 with an embedded magnetic sensor 111 and a seal 110. The sensor holder 112 is insert-molded to a metal core 115 forming the seal 110 by injection molding of synthetic resin.
The seal 110 is formed by a combination of a first seal ring 113 and a second seal ring 114. The first seal ring 113 includes a metal core 115, formed of a rigid ring, and a sealing member 116 mounted on the metal core 115. The metal core 115 has a cylindrical portion 115a to be fit into the end of the outer member 101. An outer flange portion 115b extends radially inward from the cylindrical portion 115a. A cylindrical portion 115c, that prevents entry of water, extends axially toward the inner side from the flange portion. An inner flange portion 115d extends radially inward from the cylindrical portion 115c. A sealing member 116 is adhered on the inner circumference of the inner flange portion 115d. 
The second seal ring 114 includes a slinger 117, with a substantially L shaped cross-section, mounted onto the inner ring 106, and a pulser ring 118, fit onto the slinger 117. The slinger 117 has a cylindrical portion 117a press-fit onto a smaller diameter portion 106b of the inner ring 106. A flange portion 117b extends radially outward from the cylindrical portion 117a. An elastic seal 119 is mounted on the cylindrical portion 117a of the slinger 117. The elastic seal 119 has an axial lip 119a in sliding contact with the end face of the inner ring 106.
The pulser ring 118 includes an annular supporting member 120 and a magnetized member 121. The supporting member 120 has a smaller cylindrical portion 120a press-fit onto the cylindrical portion 117a of the slinger 117. A connecting portion 120b extends radially outward from the smaller cylindrical portion 120a. A larger cylindrical portion 120c, extending from the connecting portion 120b, is fit onto the larger diameter portion 106c of the inner ring 106. The magnetized member 121 is adhered to the larger cylindrical portion 120c. The magnetized member 121 is made of rubber or synthetic resin mingled with magnetic powder. N and S poles are alternately arranged along the magnetized member 121. The magnetized member 121 is arranged opposite to the magnetic sensor 111 so that it does not contact the cylindrical portion 115c of the metal core 115.
The sealing member 116 includes a side lip 116a, a pair of radial lips 116b, 116c and a side lip 116d. The side lip 116a of the slinger side slidingly contacts the flange portion 117b of the slinger 117. The pair of radial lips 116b, 116c slidingly contacts the smaller cylindrical portion 120a of the supporting member 120. The side lip 116d of the pulser side slidingly contacts the connecting portion 120b of the supporting member 120.
The sensor holder 112 is arranged opposite to the end face of the outer member 101. An annular recess 122 is formed to expose a portion of the cylindrical portion 115a of the metal core 115. O ring 123 is elastically mounted within the recess 122. A disc shaped cover 124, formed with an aperture having a diameter smaller than that of the slinger 117, is mounted on the inner side end face of the sensor holder 112.
The entire structure including the O ring 123 of the wheel speed detecting apparatus 104 can be previously assembled by first combining the first seal ring 113 and the pulser ring 118. The supporting member 120 of the pulser ring 118 is then press fit onto the slinger 117. This sub-assembly is axially pushed so that the cylindrical portion 115a of the metal core 115 is fit into the outer member 101. The cylindrical portion 117a of the slinger 117 is simultaneously press-fit onto the smaller diameter portion 106b of the inner ring 106. Such a structure makes it possible to prevent separation between the metal core 115 and the sensor holder 112 as well as the entry of water from the interface between the metal core 115 and the sensor holder 112. Reference Patent Document: No. 183701/2006.
However, in the prior art wheel bearing apparatus 100 incorporating a wheel speed detecting apparatus 104, it is believed that the synthetic resin insert molded sensor holder 112 would separate from the metal core 115 that forms the first seal ring 113 when the wheel bearing apparatus is used under severe running circumstances such as subjected to splashes of muddy water or salty water or repeated high or low temperature. The separation between the metal core 115 and the sensor holder 112 causes variation in the air gap between the magnetic sensor 111 and the magnetized member 121. Thus, this makes exact speed detection impossible.
Also in the prior art wheel bearing apparatus 100, even though the wheel speed detecting apparatus 104 is protected by the disc shaped cover 124 mounted on the sensor holder 112 and the detecting portion is sealed by the seal 110, it is believed that muddy water will solidify on the slide contacting portion of the seal 110. This causes abnormal wear of the sealing member 116 when muddy water enters over the disc shaped cover 124 and dwells in the seal 110. This detracts from the sealing performance. Thus, it is difficult to assure the reliability of the bearing for a long term.
In addition in the prior art wheel bearing apparatus 100, the sensor holder 112 is displaced from the outer member 101 when it is used under conditions where shock or vibration is applied to the apparatus 100. This would not only detract from the sealability of the fitting portions and the seal 110 but makes exact detection of the wheel speed impossible. The sensor holder 112 with the metal core 115 is fit into the outer member 101. The metal core is in with metal-to-metal contact. Thus, the fitting strength will be increased by improving the surface roughness and dimensional accuracy of the fitting portion. However improvement of the surface roughness and dimensional accuracy of the fitting portion also increases the number of manufacturing steps and management steps and thus reduces the cost effectiveness.
In the prior art wheel bearing apparatus 100, a connector portion 112a, for a harness (not shown) connecting the magnetic sensor 111 and a control means (not shown) mounted on a body of the vehicle, is integrally molded with the annular sensor holder 112 at a lower portion. Thus, output signals from the magnetic sensor 111 are sent to the control means by connecting a plug of the harness to the connector portion 112a. 
During mounting of the wheel bearing apparatus 100 to a vehicle after the wheel speed detecting apparatus 104 has been mounted on the outer member 101, the wheel bearing apparatus 100 might be erroneously handled and hung from the connector portion via the harness. It is believed that such a handling of the wheel bearing apparatus 100 would cause the plug to be dislodged from the connector 112a. Additionally, the antilock braking system could not operate normally. Further, the sensor holder 112 would be dislodged from the outer member 101 if the metal core 115 mounted on the outer member 101 is displaced.
Finally in the prior art wheel bearing apparatus 100, the magnetic sensor 111 and the magnetized member 121 are oppositely arranged via the cylindrical portion 115c of the metal core 115. Thus, it is difficult to obtain high detecting accuracy and reliability. The detecting accuracy and reliability are detracted by the presence of the metal core between the magnetic sensor and the magnetized member.